WBC Counting Research Articles

A national quality assessment scheme for counting residual leucocytes in unfixed leucodepleted products: the effect of standardisation and 48 hour storage

Background. WBC counting, an essential part of quality monitoring of WBC-reduced blood components, is carried out logistically within 48–72 h of collection. The between-laboratory variability and effects of 24–48 h storage were investigated using three major counting technologies. Study design and methods. Samples of RBC and platelets with WBC in the range 0–50/μl were transported by courier. WBC counting was performed on days 1 and 2, by IMAGN 2000, flow cytometry and Nageotte, initially using local protocols and then using a national flow protocol. Up to 15 laboratories participated in each exercise. Results. For “real failed leucodepleted” red cell products, higher levels of variability were observed for flow and Nageotte, as compared to IMAGN. For spiked RBC samples at critical decision making point (3–20 WBC/μl), between-laboratory the coefficients of variation (CVs) were low for IMAGN and were the highest for Nageotte. Flow cytometry CVs were generally high but improved subsequent to standardisation of sampling and the gating strategy. A similar pattern in the variability of results was observed for platelet concentrates. Sign tests using all samples (carried out for each method in each exercise; 25 in total) demonstrated no overall tendency for larger WBC counts to be recorded on day 1 when compared to day 2, although this difference was significant ( p<0.001) in certain cases depending on the nature of the spiked product. Conclusions. We conclude that while a good performance is achieved using validated automated technologies for low residual leucocyte counting, the unification of reagents and standardisation of sampling and gating strategies are essential in obtaining interchangeable results. Unfixed RBC and platelet samples can generally be stored for 48 h before WBC counting.

A platelet quality assessment scheme for comparing the performance of quality monitoring laboratories in the UK National Blood Service

This exercise focused on performance of NBS quality monitoring establishments with respect to enumeration of low leucocyte and other quality indexes of platelet concentration. Paired identical leucodepleted platelet samples, spiked with WBC ( 20 cells/ μl ) in `vacuette' or `pouch' were assessed by participants ( n=20) on days 1, 2 and 5. For low WBC counting, all laboratories gave estimates within acceptable range (±25%) and good agreement between storage and assay methods was observed on days 1 and 2. Day 5 results showed greater variability. Under improved performance criteria (±15%), only one laboratory under-estimated at days 1 and 2. Similarly, other parameters demonstrated good agreement between storage methods on days 1 and 2. At day 5, mean results were often significantly different to previous days. Improved performance target (±15%) will allow identification of non-conformers.

Effect of concurrent experimentally induced bovine respiratory syncytial virus and bovine viral diarrhea virus infection on respiratory tract and enteric diseases in calves

Abstract Objective To compare experimentally induced concurrent bovine viral diarrhea virus (BVDV) and bovine respiratory syncytial virus (BRSV) infection with single virus infection. Animals 9- to 12-month-old calves. Procedure Calves were allotted to 4 groups: 1, mock-infected control (n = 3); 2, BRSV infected (5); 3, BVDV infected (5); and 4, concurrent BRSV and BVDV infected (5). Total and differential WBC counting was done. Concentration and duration of BVDV in nasal secretions and serum, and duration of BRSV in nasal secretions were determined. Concentration of BVDV in various tissues was determined, and isolation of BRSV from lung tissue was attempted. Histologic examination and immunohistochemical analysis were done to detect lesions and distribution of viral antigens, respectively. Results Calves with concurrent infection developed more severe clinical signs of disease (fever and diarrhea), leukopenia, and more severe lesions. They also shed virus from nasal secretions in greater concentration and for longer duration, and BRSV was isolated from their lungs. Calves with concurrent infection also had more extensive lung lesions. Alimentary epithelial necrosis and severe lymphoid depletion were associated with BVDV infection in calves with or without concurrent BRSV infection. BVDV antigen in lymphatic tissue was detected in stromal cells only. Conclusions Concurrent infection with BRSV and BVDV resulted in more severe respiratory tract and enteric disease than did infection with either virus alone, possibly indicating synergistic effect between the viruses. BVDV’s role in causing respiratory tract disease is attributable, indirectly, to effects on the host’s immune system, not to infection of the lungs. (Am J Vet Res 1998;59:1423–1430)

Rapid accurate absolute granulocyte count determination during severe leukopenia using the flow cytometer

The absolute granulocyte count (AGC) in 125 blood samples from patients with total white blood cell counts of less than 1,000/microliter was estimated using three different methods, which were then compared for efficiency and accuracy. The three methods were 25 cell differential counts using Wright's-stained blood smears, granulocyte percentage estimates from WBC counting chambers, and combined narrow- and wide-angle light-scatter characteristics determined on a flow cytometer. A survey of clinical laboratories at University Hospital Cancer Centers revealed that the smear differential was the most-often-used method in those laboratories even when less than 25 cells could be counted. Consequently the data obtained from the counting chamber and flow cytometer methods were compared to the smear differential "standard" using linear regression, and outliers were identified. There was good correlation between AGC determined by smear differential and WBC counting chamber (correlation coefficient .911) and excellent correlation between the AGC determined by smear differential and the flow cytometer method (correlation coefficient .970). The flow cytometer method used in this investigation required minimal specimen preparation, and test results were available at a rate of 60 seconds/sample. The ease of sample preparation, speed, and statistical reliability of test results makes the flow cytometer an attractive alternate method of determining granulocyte counts on leukopenic patients as compared to the stained blood smear differential.